During the past year, the VRC's Vector Core created and tested new vaccine vectors expressing novel forms of envelope proteins. In addition, work continued to test different methods and routes of administration as well as prime/boost combinations to further optimize HIV vaccine strategies. DNA, VLP, nanoparticles and other vectors were tested. Several candidate vaccines that elicited promising immunogenicity data in preliminary studies are being tested further. Studies to understand development of broadly neutralizing antibodies using germline knock-in mice have been started. These studies are testing novel immunogens designed to engage germline genes for VRC01 and other CD4 binding site bnAbs. Epitopes recognized by vectors expressing neutralizing antibodies were also analyzed and tested for their ability to induce similar types of antibodies, in vivo.